1. Field of the Invention
The present invention relates to a sheet feeding apparatus applied to a recording system such as an ink jet recording system.
2. Description of the Related Art
In the past, a recording system which records an image on a recording medium (referred to as "recording paper" or to merely as "paper" hereinafter) such as a paper, OHP sheet or the like has been proposed to have a recording head of various recording types. The recording heads include a wire dot recording head, heat-sensitive recording head, heat transfer recording head, ink jet recording head and the like.
Among these recording heads, particularly, the ink jet recording head which directly ejects or discharges ink onto a recording paper is noticed in the point that a running cost thereof is inexpensive and a recording operation thereof is noiseless.
In such an ink jet recording system, as one of inherent constructions required due to the recording with the use of the ink, for example, a spur roller (refer to merely as "spur" hereinafter) constituting a sheet ejecting mechanism is used.
The spur is generally disposed, together with an ejector roller, at a downstream side of a recording head in a recording sheet feeding path and cooperates with the ejector roller to feed the recording sheet. That is to say, the recording sheet is pinched between the ejector roller and the spur to be moved. In such feeding of the recording sheet, the spur urges the recording sheet against the ejector roller, and the rotating ejector roller feeds the recording sheet by the use of a friction force created between the ejector roller and the recording sheet due to such urging force. In this case, the spur is arranged or disposed to contact a recorded surface (i.e., inked surface) of the recording sheet. Thus, the spur is constituted by a thin plate-shaped toothed wheel so that the contacting area between the spur and the recording sheet is minimized as long as possible, whereby the ink which may stick to the spur does not influence the recording sheet or other elements as long as possible.
However, if the environment where the ink jet recording system is used has a relatively high humidity, the spur may contact the inked surface of the recording sheet before the ink has not yet been fixed to the sheet completely, with the result that a relatively large amount of ink sticks to the spur, from which arises a risk that the recording sheet or other elements are smeared with the ink. Further, if an image having high density of pixels such as graphics or a color image is recorded on the recording sheet, since the relatively large amount of ink is transferred onto the recording sheet, the problem as mentioned above will occur. Further, recently, since the bubble jet recording head has particularly been made small-sized, the recording system itself tends to become compact. In this case, since the sheet feeding path is shortened, it is difficult to improve the fixing of the ink.
On the other hand, there remains room for improving the spur itself with regard to the conveying feature of the recording paper and the positional accuracy in association with the ejector roller and the platen. For example, the recent ink jet recording system is sometimes designed so that it can accommodate various recording papers such as normal recording papers, thicker envelopes or the like; in this case, the spur, ejector roller and platen must be designed and arranged so as to provide proper feeding of the sheet in dependence upon the various recording papers. Further, when the recording system is made small-sized, a member for supporting the spur often serves as another member constituting the recording system such as a cover of the recording system; in this case, the positional accuracy of the member will be important.